Motion-picture projector



April 20, 1948. R. J. MaLLi-:R 2,439,98l

MOTION PICTURE PROJECTOR Filed Feb. 2l, 1941 2 Sheets-Sheet l INVENTOR. @QV/wwf@ JMMLE@ April 20, 1948.

R. J. MILLER MOTION PICTURE PROJECTOR Filed Feb. 2l, 1941 2 Sheets-Shee 2 Patented Apr. 20, 1948 UNITED STATES PATENT OFFICE MOTION-PICTURE PROJECTOR Raymond J. Miller, Detroit, Mich., assigner to American Pattern and Manufacturing Co., Detroit, Mich., a copartnership Application February 21, 1941, Serial No. 379,962

2 Claims. 1

This invention relates to motion picture projectors and more particularly to improved means for cooling the lm.

In modern motion picture projectors, independent visual images carried by a strip of lm are successively aligned with an aperture and are projected onto a screen by means of a light directed through the aperture and lm in such a manner as to create the illusion of motion.

The lm may be formed of Celluloid or any other relatively transparent material having the desired qualities of exibility and durability.

The light employed to project the images from the film onto the screen may emanate from any suitable light source and is directed towards the lm aperture in such a manner that the rays of light follow a substantially conical path decreasing in diameter as the aperture is approached. The rays of light become more concentrated as the diameter of the cone decreases and the heat per unit of area increases proportionately.

When the images of the iilm are in alignment with the aperture and are projected onto the screen, the film is subjected to the full heat intensity of the light. Due to the inflammable nature of the materials heretofore found suitable for projector film, a considerable re hazard is involved.

An object of this invention resides in the provision of novel means to dissipate heat from the projecting light.

A further object oi the invention is to propel a sheet of cooling air across the aperture plate and lm to cool the portions of the projector subjected to the heat thereof.

Another object is to provide an improved impeller to force cooling air across the members in such a manner that they are effectively cooled and the light source is not subjected to disturbing air currents.

A still further object of the invention resides in the provision of air propelling means carried by a shutter driving member to move air across an aperture plate between the shutter and the lm to dissipate heat.

Yet another object of the invention is to provide a motion picture projector having improved shutter and iilm Ventilating means to absorb heat with minimum interference with the light.

Another object is to provide an aperture and film cooling compartment isolated and substantially sealed from the film compartment in such a manner that dust and dirt are effectively excluded from the film compartment thereby propracticed or carried out in various ways.

tecting the film guiding and driving mechanism and the projector lenses.

Still another object of the invention resides in the provision of a power driven shutter having impeller blades positioned in such a manner that heat absorbed by the shutter from the projecting light is eiectively dispelled to atmosphere.

Other objects and advantages of this invention will be apparent from the following detailed description considered in connection with the accompanying drawings, submitted for purposes of illustration only, and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

In the drawings wherein similar reference characters refer to similar parts throughout the several views:

Fig. 1 is a perspective View partly in section of a motion picture projector embodying the present invention.

Fig. 2 is a plan View partly in section of a portion of the projector illustrated in Fig. 1.

Fig. 3 is a sectional View taken substantially on the line 3-3 of Fig. 2, looking in the direction of the arrows.

Fig. 4 is a sectional view taken substantially on the line 4-4 of Fig. 2, looking in the direction of the arrows.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

Referring to Fig. 1, it will be observed that the invention is illustrated as being embodied in a motion picture projector wherein a plurality of separate visual images are carried by a strip of Celluloid or other suitable film material I0. In one form of projector used commercially in theaters, the film ID is approximately thirty-rive millimeters in Width, and the separate images are carried by a plurality of substantially equally spaced successive frames. Where the thirty-iive millimeter lm is employed it has been found that very desirable results are obtained where sixteen separate frames are provided in a foot of lm.

Means such for example as an intermittently driven sprocket may be provided to intermittently move the film I between upper and lower feed sprockets I2 and I4 to intermittently position succeeding frames of the lm into alignment with an aperture I6 formed in an aperture plate I8. Light from a suitable source is directed to impinge on the aperture plate I8 and pass through the aperture I6 and the film I il to project the image from the ilm onto a screen so positioned asl for example in a theater, to beviewed.

In the thirty-ve millimeter lm generally used for commercial projection the film I is provided adjacent each frame with four sprocket; receiving apertures or holes 2B to receive sprocket teeth 22 extending lradially at the outer edges of the' driving sprockets I2 and I 4 and an intermittently driven sprocket whereby the lm I 0 may be moved to position successive frames of` iilmV into alignment with the aperture I6. Each of the lm driving sprockets is preferably provided with sixteen driving teeth 22 on each side and thus moves four frames of the nlm in one complete revolution'.

The film may move at any predetermined speed. However, it has been found that. besty results` are obtained fromvthe. sound equipment nowconventionally used with motionl picture projectors when the lm is driven at av speed of approximately ninety feet or 1440 frames per minute, that is, at the rate of one and one-half feet or 24 frames per second.

To drive the film at this speed the intermittence drive sprocketl must be actuated 144:0 timesper minute, making a-quarter revolutioncach time it is actuated, and the upper and lower feed sprockets I2 and Idimust be continuously driven at a speed of 360 R. P. M.

One complete revolution of the intermittently driven sprocket will move four frames, and since this sprocket makes six complete revolutions per second, it must be actuatedl through a.` complete cycle each gli of a second. This cycle mustbe further subdivided since aninterval of time is required to move the hlm'. Good results havebeen obtained where thisA cycle is divided` intoY five equally spaced time intervalsof 1/izo of a second each. One of these time intervalsof 1/izc of a secondmay be utilized to-v actuate the intermit tently driven sprocket'to position thenext succeeding frame of the film in alignment Withthe aperture I5, and each individualframe. may be maintained in alignmentvvith the aperture theremaining 4/izo of a second: of each cycleof fofa second topermit light from. a suitable source to pass through the aperture I6 and` lm` I0. to project the image from the lmontothe-screen.

A shutter such for example asa rotatable blade 24 is provided to intermittently interrupt the iiowv of, light through the iilmv I0. and aperture I6l to prevent the images on the screen frombecoming blurred or streaked as the intermittently drivenv sprocket moves successive frames of the. lm Ill' rupting the projecting light to prevent visible.

flicker or to shield movement of the lm. Each frame of the lmis therefore-subjected directly to the heat of the light, for approximately 1/48 of. a secondwhile it is. aligned with the, aperture I6, and. in addition is subjectedto heat conductedto it through. the aperture plateV I8. In view` ofthe fact that the lm I0 is made of. inflammable ma.-

terial, a considerable re hazard is thus involved. The component elements of the projector may be carried by a main housing 26 having front and back walls 28 and 30 respectively and an intermediate wall 32 dividing the space Within the housing 26 into transversely spaced mechanism and lm compartments 34 and 36 respectively.

The mechanism required to drive the lm sprockets I2 and Id, the intermittently driven lm feeding sprocket, and the shutter 24 may be positioned within the mechanism compartment 34. The driving. mechanism preferably includes a generally vertically extending drive shaft 38 operablyu connected to drive generally horizontally extending shafts projecting through and suitably sealed inthe inter-mediate wall 32 to prevent the escape of lubricating oil from the compartment 34 to the lm compartment 3B.

A film track carrier 40 supports the aperture plate I8 having the aperture I6 formed therein. The carrier` umay be.` supported by an aperture plate. housing 42 preferably aligned with a w-allM projecting transversely from the Wall 32;

The iilmV I0 isrpreferably guided betweenrgzuide rollersv fandmovesbetween spacedtracks 48 and shoes 50 yieldingly urged towards the tracks ii8by springs 52. The film is thus maintained in -proper alignment with the aperture I 6 and restrained from moving agreater distance than is desired each. time the intermittentlydriven sprocketV is actuated.. by the driving mechanism; associated with the flywheel 54.

The. projecting light may emanate from any suitable` source preferablypositioned behind the back wall uand the light is admitted into the lm compartment 35v through a conical housing 56y communicating. with `ashutter housing 53 having the. rotatable'shutter blade 24.therein. A re shield dei formedofY reproof material suchifor example asv asbestos may be interposed between the shutterhousing,` 5B1-annif a preferably'inward-ly extending baiiie 62.. formed in theback wall113. The baiiie 62 terminates inalight admission port 64 alignedy with the aperture Informed in the aperture plate- IB.

A. re shutter lor gate '66 mounted on-a suitable actuating traineau, more fully disclosed-in my oopending application Serial No. 250,310,1nay be provided to automatically olosethespace between the aperture I6.. and port Edfadjacent.the baiile1ii2 to interrupt the How of projectingrlight and heat to the iilm` inv the event that the projector. fails to operate at the desiredl speed. A manually operatedmember i0.A may be provided to move the fire valve 5G to the operative position illustrated in Fig. 4 when the projector is not operating.`

Anyfdesired formof shutter such` for example as those disclosed in. my (3o-pending. application Serial. No. 250,310 may beemployedto. interrupt the projecting light when the nlm i0 isheing intermittently moved to align, succeedingA film frameswiththe aperture Id. One.desirableform` includes the rotatable shutter blade 2li' mounted on ashaft. 12 and provided with a counterbalancing weight ld. The shaft Zprojects-through a suitable oilseal. It positioned in the intermediate. wall 32 and is'operably connected through suitable gearing 'In with a generallyhorizontally extending s-haft. which may drive the intermittently driven` nlm feeding mechanism including the flywheel 5E.

Means rare provided. to withdraw heat from. the

projecting light.Y and to cool the nlm, aperture plate and the associated parts of the projector subjected to heat during operation of the projector.

One desirable form of such cooling means comprises a blower 88 communicating directly with the atmosphere on one side, and communicating with the atmosphere on its other side by way of a manifold 82 and an aperture cooling chamber 84. The manifold passage 82 is formed by the intermediate wall 92 and the wall 44 aligned with the aperture plate housing 42, a portion of the back wall 80, and an extension 88 thereof. The aperture cooling chamber 84 is positioned between the back wall 30 and baffle 92 on one side. and the aperture plate housing 42, the film track carrier 49, and the aperture plate i 8 on the other side.

The blower 80 is provided with impeller blades 88 carried by a disk 90 supporting the shutter blade 24 and the counterweight 14. The blades 88 rotate in a suitable housing 92 communicating with atmosphere on one side by way of a plurality of apertures 94, which by way of example may be discharge apertures.

Cooling air may be withdrawn from the atmosphere through inlet apertures 9S formed in the back wall 30 adjacent the vertical edge of the aperture plate housing 42 adapted to be engaged by a vertically extending portion 90 of a side door |00 to seal the film compartment 35 from the aperture cooling chamber 84.

The cooling air is thus drawn from the atmosphere through the inlet apertures 96 into the aperture cooling chamber 84 where it passes across the aperture plate housing 42, nlm track carrier 40 and is directed by venturis |82 carried by the film track carrier to impinge on and cool the aperture plate I8 and nlm I Il aligned with the aperture I6. The cooling air is then propelled through the manifold 82 to the housing 92 of the blower where it is discharged to atmosphere by the blades 38 through the apertures 94. The direction of the flow of air through the aperture cooling chamber 84, manifold 82 and blower 80 is indicated by the arrows |04.

Attention is called to the fact that the iiow of cooling air is conned to the aperture cooling chamber 84 and manifold 82, and that the air within the film compartment 38 is not disturbed. The possibility of dirt entering the nim compartment to injure the delicate lm positioning and moving mechanism and the projector lenses is therefore minimized.

The flow of cooling air into, out of and through the aperture cooling chamber 84 causes virtually no disturbance of air in the shutter housing 58 because the iiow of air through the inlet apertures 96 across the chamber 84 to the manifold 82 is less restricted than it is through the shutter housing 58 and the light admission port 64 of the inwardly directed baiile B2. There is thus virtually no tendency for the cooling air to set up disturbing air currents which might interfere with the operation of the light source such for example as an arc light.

If desired, the blower may be a separate unit not associated with the shutter mechanism, and may be positioned in any convenient location to direct cooling air through the space between the aperture plate and the shutter mechanism without departing from the spirit of my invention.

A framing light I 08 preferably positioned in the aperture cooling chamber 84 may be provided to permit observation of the iilm l0 through an observation port position-ed forwardly of the aperture plate I8 to determine whether the frames of the lm are in proper alignment with the aperture I6. A switch IID having a plunger II2 positioned to be engaged by the door I00 when in the closed position may be provided to permit the light to be illuminated when the door is open and to shut it off when the door is closed.

A glass I I 4 positioned in the shutter housing 58 may be provided to permit inspection of the projecting light with reference to the nre shield 60 to facilitate adjustment of the light relative to the aperture plate I8 and aperture I6.

A channel IIS formed in the back wall 30 adjacent the baiile B2 may be provided to receive a valve member whereby the projecting light may be interrupted to facilitate changing over from one projector to another when a reel of iilm is exhausted or for any other purpose.

This a continuation in part of my cci-pending application Serial No. 250,310, iiled January 11, 1939, now Patent No. 2,312,653, issued March 2, 1943.

Features disclosed but not claimed herein are being claimed in my co-pending application Ser. No. 741,259, filed April 14, 1947, now Patent Number 2,429,364, dated October 21, 1947.

I claim:

1. In a motion picture projector, a holding, a partition separating said housing into a film compartment and a mechanism compartment, an aperture plate extending from said partition into said lm compartment, a blower having one side communicating with the atmosphere, said housing having an opening communicating with the other side of said blower in a path including said plate, a side door for said lm compartment, a portion of said door being adapted to close against the adjacent vertical edge of said plate, whereby to obstruct communication between said opening and in front and laterally of said plate.

2. In a motion picture projector, a housing, a partition separating said housing into a lm compartment and a mechanism compartment, an aperture plate extending from said partition into said lm compartment, a blower having one side communicating with the atmosphere, said housing having an opening communicating with the other side of said blower in a path including said plate, a side door for said lm compartment, a portion of said door being adapted to close against the adjacent vertical edge of said plate, and a baiile mounted on a wall of said housing and extending towards the lower edge of said plate, said partition, plate, wall, and baffle forming an obstruction between said opening yand parts in front and laterally of said plate.

RAYMOND J. MILLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,408,203 Jenkins Feb. 28, 1922 1,758,689 Del Riccio May 13, 1930 1,853,725 Dina Apr. 12, 1932 1,985,629 Crabtree Dec. 25, 1934 2,186,618 Philips Jan. 9, 1940 2,194,585 Brenkert Mar. 26, 1940 

